1. Field of the Invention
The present invention relates to radio and antenna structures and connectors, and methods of implementing them. In particular embodiments, the present invention is directed to such structures, connectors, and methods for improving signal reception and transmission by a computer-based device which utilizes the global positioning system (GPS).
2. Description of Related Art
Today's compact and portable computers provide users with readily available computing capabilities at a moment's notice. However, this ready mobility of portable computers brings with it the uncertainty of location. There may be instances when a mobile user's location must be quickly determined. Tracking a user's location may be important, for example, to avoid potential danger in unfamiliar areas, for automatic vehicle location, and for marine, aviation and industrial applications, among others. Accordingly, the space-based navigation techniques of the GPS have been found to be important for assisting computer-users in determining their particular locations and directing them toward their desired destinations.
The GPS is a space-based radio navigation system that provides worldwide, all-weather determinations of position, altitude, time and velocity. The GPS is implemented using a passive radio receiver and is available to a virtually unlimited number of users. The GPS radio receiver detects and receives precise reference signals from a constellation of 24 GPS satellites orbiting the earth. Low cost GPS receivers have been available for several years in specific GPS-dedicated products. Typically, these GPS application-specific products have included such basic computer components of a display, Keyboard, power supply, processor and housing. Accordingly, it has been recognized that portable computers and the like are an excellent platform to utilize GPS technology.
Several methods have been devised to install and incorporate the hardware and software supporting GPS technology into portable computers. One method uses a Personal Computer Memory Card International Association (PCMCIA) format provided by a PCMCIA slot-equipped host computer. By taking advantage of the easily installable and removable features of PC cards within PCMCIA slots, GPS capabilities may be activated and used by almost anyone having access to a laptop-type computer or personal digital assistant (PDA). The packaging of a GPS receiver in the PCMCIA format, however, necessitates a format compliant with the PCMCIA standard. Accordingly, a streamlined GPS receiver RF front-end construction is desirable to contain the GPS product within the PCMCIA port.
Antenna placement, however, has been found to raise certain issues with regard to the particular positioning configuration of the antenna to maximize visibility of the antenna to the GPS satellites, yet minimize cumbersome external components and cables. Although such considerations are evident in a variety of wireless communications applications, an effective antenna placement and mounting structure has yet to be developed which provides for both simple and easy mounting and removal, while concurrently maximizing signal reception and quality.
Furthermore, the maximization of the signal reception level and the minimization of external noise and interference has been found to be a design challenge. To interconnect multiple electrical and electronic devices, such as an antenna to a radio, cables or other wiring schemes are typically implemented between the devices. For example, the coupling of an antenna to a radio to radiate or receive radio waves generally requires the use of a coaxial cable with RF connectors. Associated coaxial connectors may be necessary to connect the radio and antenna to the coaxial cable.
Coaxial cables, however, tend to introduce undesirable signal degradation attributable to signal attenuation through the cable, added receiver system noise, as well as reflection losses attributable to mismatched impedances. Reflection losses are apparent transmission losses across the cable which result when the impedance of a load, e.g., an antenna, is mismatched with that of a generator, such as a radio transmitter. Consequently, transmission losses on the line result when a portion of the energy is reflected due to the discontinuity of the mismatched impedances in the transmission line.
More particularly, referring to the GPS environment, a conventional cable configuration may include a GPS radio receiver 100 coupled to a PCMCIA interface 102 via a cable arrangement, as illustrated in FIG. 1. The PCMCIA interface 102 is coupled to the GPS receiver 100 by a serial interface port cable 104. A patch-type antenna 106 is coupled to the receiver 100 via a coaxial cable and connector arrangement 108. According to device specifications, this coaxial cable arrangement 108 may introduce reflection and transmission losses of approximately 2.5 dB to 5 dB maximum at 1575 megahertz (MHz). However, since GPS satellite signals are transmitted within a dynamic range between 50 dB down to approximately 30 dB, the inherent 5 dB cable loss would significantly degrade the signal level at the 1575 MHz GPS receiver frequency. Furthermore, if physical obstructions such as foliage or buildings are present, the signal strength could be even further weakened.
These losses can be significant, seriously affecting the intensity or amplitude of the received signals, and thus the ultimate acquisition of the desired signals. Moreover, if poor impedance matching or other factors cause the carrier-to-noise ratio to be particularly low, the radio receiver may not be sufficiently sensitive to pick up any radio signals falling within the desired dynamic range. As a consequence, extensive signal amplification and other electronic hardware may be necessary to increase the carrier-to-noise ratio. Signal amplification, however, may be difficult to incorporate in certain applications due to the limited availability of space to accommodate the necessary electronic hardware.
In addition, the mere physical presence of the coaxial cable, as well as the serial interface cable coupling the GPS receiver to the PC card, may present difficulties in certain applications, particularly if a lengthy amount of cabling is required. Loose cables may get caught on objects or other obstacles, leading to potential disconnection, or perhaps interfering with other equipment. Thus, not only do cables introduce signal attenuation and losses, but loose cables also create possibly hazardous physical obstructions and potential breakage of the communication line.
Furthermore, in addition to the signal degradation caused by the separate components (e.g., the PCMCIA interface card, intermediate serial port connector cabling, receiver, coaxial cable and connector assemblies, and antenna), these components also require individual maintenance in proper operating condition. Consequently, in addition to the increased potential for breakage or loss of one or more of the associated elements, the cost of maintenance and repair or replacement of the individual components could become quite expensive and impracticable.